I'm not sure how they classify levels of residential care in NY, but they may be talking about a PRTF or psychiatric residential treatment facility. These are secure units and are more medically intensive as they will have a nurse practitioner on staff at all times, more advanced staff available around the clock and the kids will see the psychiatrist much more frequently.
My daughter is at a similar program now - it is a 6 month program. In our state a judge has to meet with the psychiatrist and parents to rule that they agree on a length of stay based upon the child's history and current condition.
The kids usually have more complex issues with multiple diagnoses and do require longer terms of stay before being assessed as ready to transition to a lower level of care (non-secure).